This section provides background information related to the present disclosure which is not necessarily prior art.
Examples of infrastructure antenna systems include customer premises equipment (CPE), satellite navigation systems, alarm systems, terminal stations, central stations, and in-building antenna systems. With fast growing technologies, antenna bandwidth has become a great challenge along with the requirement to miniaturize CPE device size or antenna system size in order to maintain a low profile. In addition, multi-antenna systems having more than one antenna have been used to increase capacity, coverage, and cell throughput.
Also with fast growing technologies, many devices have gone to multiple antennas in order to satisfy the end customers' demand. For example, multiple antennas are used in multiple input multiple output (MIMO) applications in order to increase user capacity, coverage, and cell throughput. With the current market trend towards economical, small, and compact devices, it is not uncommon to use multiple antennas identical in form that are placed in very close proximity to each other due to size and space limitations. Moreover, antennas for customer premises equipment, terminal stations, central stations, or in-building antenna systems, must usually be low profile, light in weight, and compact in physical volume, which makes Planar Inverted F-Antennas (PIFAs) particularly attractive for these types of applications.
FIG. 1 illustrates a conventional Planar Inverted F-Antenna (PIFA) 10. As shown in FIG. 1, this basic design consists of a radiating patch element 12, a ground plane 14, a shorting element 16, and a feeding element 18. The width and length of the radiating patch element 12 determines the desired resonant frequency. The summation of the width and length of the radiating patch element 12 is about one quarter wavelength (λ/4). The radiating patch element 12 may be supported by a dielectric substrate above the ground plane 14.